Conventional touch screen computing devices have been configured to identify the positioning and/or movement of one or more fingers or other objects on or near touch surfaces of the devices. For example, touch screens associated with some touch computing devices have been configured for receiving input via finger gestures and to perform one or more functions in response to those finger gestures. Certain touch screen computing devices can receive input from input devices such as stylus devices. A stylus is a writing, drawing, or pointing instrument or utensil that is generally configured to be hand-held and, in the context of touch screen computing devices, used to interact with a touch surface. For example, touch screen computing devices have identified input based on one end of the stylus moving on or near the touch surface of the computing device. Styli (or styluses) have been used with personal digital assistant devices, tablet computing devices, smart phones, and other touch screen computing devices for handwriting, drawing, selecting icons, and providing other forms of input to such touch computing devices.
Some styli include a radio, a wireless transceiver, or other means for wirelessly communicating with touch computing devices. Some styli include a light emitting diode (LED) or other means to indicate that the stylus is powered on or communicating with a touch computing device. Such features require power, and because styli are typically wireless, power is supplied by internal batteries within the styli. As a result, styli with internal electronics require their own, internal power supply. Prior solutions involved incorporating user-replaceable batteries, such as AAA and AAAA-sized cells, into styli. However, the relatively larger size and weight of replaceable batteries as compared to captive batteries necessitate larger and heavier styli. Elongated and tubular input devices such as styli that use cylindrical, replaceable batteries, such as AAA and AAAA cells, have wider bodies than more slender writing and drawing instruments, such as traditional pens and pencils. The increased width and weight of such input devices does not ergonomically enhance their use as styli and may cause discomfort during extended periods of use. In addition to adding size and girth to styli, many replaceable batteries are not rechargeable and must be periodically replaced. In cases where rechargeable, replaceable batteries are used in a stylus, such batteries typically need to be removed from the stylus in order to be charged outside of the stylus in a battery charger.
In order to address the size and weight issues implicit in use of traditional replaceable batteries, some styli are powered by relatively smaller, slenderer captive batteries. Because such captive batteries are not user-replaceable, these styli cannot be used without being periodically recharged. Regardless of whether a stylus uses a replaceable or captive battery, prior solutions for charging a stylus include using a wired connection between a stylus and a power source via a, plug, port, or receptacle built into the stylus or including magnetic materials in the stylus so that the stylus can be magnetically coupled to a power source. While these traditional techniques allow the stylus to connect via a wired or magnetic connection to a power source, they add unwanted weight and size to the stylus. Another technique for charging or recharging mobile devices is inductive charging using wireless, inductive coupling between an inductive charging station or mat and a device having a battery to be charged. However, inductive charging may not be feasible for devices with metal housings or cases. For example, a metal housing for a stylus body may interfere with wireless, inductive power transfer. Inductive charging requires inclusion of an induction coil within the device whose battery is being recharged. Some inductive coupling techniques use magnets and magnetic material within a device to be charged to ensure that the device remains in close enough proximity to the power source to be inductively charged. Each of these charging technologies and techniques have the drawbacks of adding size and weight to the devices being charged, thus making them less aesthetically pleasing and not ergonomically enhancing their use as styli. In addition, incorporating magnetic materials and induction coils into styli can interfere with electronic components, including wireless transceivers, contained within some active styli.